What are the necessary steps in a workup before starting a patient on lithium?

Comprehensive Workup Before Starting Lithium Therapy

Before initiating lithium therapy, a thorough baseline assessment including renal function tests, thyroid function tests, electrolytes, complete blood count, pregnancy testing, and ECG is mandatory to ensure patient safety and optimize treatment outcomes.

Laboratory Tests Required Before Starting Lithium

Essential Baseline Laboratory Tests:

• Complete Blood Count (CBC) 1
• Renal Function Tests 1, 2, 3:
  • Blood Urea Nitrogen (BUN)
  • Serum Creatinine
  • Estimated Glomerular Filtration Rate (eGFR)
  • Urinalysis
• Thyroid Function Tests 1, 2:
  • Thyroid Stimulating Hormone (TSH)
  • Free T4
• Electrolytes 2:
  • Sodium (particularly important as hyponatremia increases lithium toxicity risk)
  • Calcium (baseline calcium level needed due to risk of hyperparathyroidism) 4
• Pregnancy Test for women of childbearing potential 1, 3

Additional Recommended Tests:

• Electrocardiogram (ECG), especially in patients >40 years or with cardiac risk factors
• Parathyroid Hormone (PTH) level 4
• Serum Calcium (to establish baseline before potential lithium-induced changes) 4

Clinical Assessment Components

Medical History Focus Areas:

• Renal Disease History: Lithium is contraindicated in significant renal disease 3
• Cardiovascular Disease: Significant cardiovascular disease is a relative contraindication 3
• Medication Review: Identify potential drug interactions, especially:
  • Diuretics (increase lithium toxicity risk) 3
  • NSAIDs (can increase lithium levels)
  • ACE inhibitors and ARBs (can increase lithium levels)
• Hydration Status: Dehydration increases lithium toxicity risk 2, 3
• Neurological Conditions: Pre-existing neurological conditions increase toxicity risk 2

Physical Examination Elements:

• Weight and BMI: For baseline monitoring of potential weight gain 4, 5
• Blood Pressure: Baseline cardiovascular assessment
• Neurological Examination: To detect any pre-existing tremor or other neurological signs

Patient Education Requirements

• Medication Schedule: Once-daily dosing (preferably evening) may improve adherence and reduce side effects 6
• Side Effect Awareness: Common side effects include thirst, polyuria, tremor, nausea 5
• Toxicity Warning Signs: Teach patients to recognize early signs of toxicity (vomiting, diarrhea, drowsiness, muscular weakness, ataxia)
• Hydration Requirements: Maintain adequate fluid intake and sodium intake 2, 3
• Medical Alert Bracelet: Patients should wear medical alert identification 2
• Monitoring Requirements: Explain need for regular blood tests

Initial Dosing and Monitoring Plan

Initial Dosing Strategy:

• Starting Dose: 300mg once or twice daily, lower in elderly or those with reduced renal function 7
• Age-Based Dosing 7:
  • Age <40: 25-35 mmol (925-1300 mg) daily
  • Age 40-60: 20-25 mmol (740-925 mg) daily
  • Age >60: 15-20 mmol (550-740 mg) daily

Early Monitoring Schedule:

• Serum Lithium Levels: Check twice weekly during acute phase 3
  • Draw blood 12 hours after last dose for accurate trough level 3, 7
  • Target level: 0.6-1.2 mEq/L for maintenance therapy 3
• Follow-up Laboratory Tests: After 1-2 weeks of treatment
  • Renal function
  • Electrolytes
  • Lithium level

Long-term Monitoring Plan

• Lithium Levels: Every 2 months during stable maintenance therapy 3
• Renal Function: Every 3-6 months 1
• Thyroid Function: Every 3-6 months 1
• Calcium/PTH: Periodically due to risk of hyperparathyroidism 4
• Weight: Monitor regularly due to potential weight gain 4, 5

Common Pitfalls to Avoid

1. Failure to adjust dose based on renal function: Lithium clearance decreases with age and renal impairment 7, 8
2. Inadequate patient education: Poor understanding of side effects leads to non-adherence
3. Ignoring drug interactions: Particularly with diuretics, NSAIDs, and ACE inhibitors
4. Overlooking hydration status: Dehydration significantly increases toxicity risk 2, 3
5. Inconsistent blood draw timing: Lithium levels should be drawn 12 hours post-dose 3, 7
6. Neglecting calcium monitoring: Hyperparathyroidism is a recognized complication 4

By following this comprehensive workup protocol, you can maximize the safety and efficacy of lithium therapy while minimizing the risk of adverse effects and toxicity.